When outbound calls are placed via the adapter, the user hears two ring tones superimposed, one on top of each other. The ringing audio produces a phasing beat, as the two tones are not perfectly in tune with one another (musicians will know what I am talking about). After the call is answered, the voice quality is perfect with no adverse effects.
My unproven theory is that once the last digit is dialed, the ATA allows immediate audio pass-through and simultaneously supplies local ringing until SIP indicates answer supervision. Does anyone else notice this, and has anyone solved it?